Fireplaces with a prefabricated combustion chamber for combustion of natural, propane or other such gases are known. These fireplaces may be either inserted into existing conventional masonry fireplaces or may be installed and subsequently framed within the structure of the building, with the combustion chamber vented into a flue or chimney. A facade is installed so that the exterior has visual appeal. The heating and visual effects of the fireplace per se are provided by means of a gas burner which simulates a conventional wood fire, with the combustion conditions being carefully controlled.
In fireplaces in which combustion products from the burner are conveyed to the flue, a supply of air may be provided to the flue to ensure that there is a constant flow of combustion products from the combustion chamber into the flue and also to dilute the combustion products to reduce condensation in the flue. Air may also flow into the combustion chamber. Fireplaces for the burning of combustible gases, with combustion products being conveyed from the burner to the flue, are described in U.S. Pat. No. 5,313,932 of H. H. Rieger and C. Adamson.
Other types of fireplaces are known as vent-free appliances, in which case the fireplace is operated without the need to vent combustion gases.
In the combustion chamber of the fireplace, it is common to simulate a wood fire by placing logs made from a ceramic material above the gas burner. The logs are normally painted to resemble a log, and are arranged to simulate logs on a wood fire. The logs are located on a ceramic grid through which combustible gas admixed with air passes and is ignited. The resultant flame tends to heat the ceramic log material to a red glow, thereby causing the visual effect of a wood fire. Fireplaces typically use a flame that is relatively static throughout its length and does not vary significantly with time.
In the present application, the flames of the fireplace may be described as a blue flame or a yellow flame, which describes the visual nature of the flame.